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Process Simulation Essentials
www.chemstations.comSlide2
If there are additional topics within the presentation slide deck or the simulation examples that you would like to see addressed, let us know.
If you would like to share any materials you have with other professors, Chemstations can either be a reference or a repository.
How can we help more?Slide3
What are we going to cover today?
What does a process simulator do?Best PracticesCommon MistakesSlide4
What does a process simulator do?
Heat and mass balances around unit operations & whole processesCalculation of what happens with vapor, liquid, solid in unit operations – cooling, heating, separating or changing phaseSlide5
Mass & Energy BalanceSlide6
What does a process simulator do?
Heat and mass balances around unit operations & whole processesCalculation of what happens with vapor, liquid, solid in unit operations – cooling, heating, separating or changing phaseHave databanks of
physical
properties of chemicalsthermodynamic models for vapor-liquid equilibria mathematical models for common unit operationsSlide7
Databank, Equations, Unit OpsSlide8
What do engineers do with process simulators?
Model existing facilities Parts or whole plantsTroubleshoot issuesOptimize energy/material use & costsIncrease throughput
Study
what happens if conditions are different Connect to control system for monitoring / controlDesign new facilitiesSlide9
Best Practices
Start with good physical property dataChoose & validate your thermodynamic modelBuild model one step at a timeHandle recycles with careSlide10
Start with good physical property data
Which heat capacity curve is correct?Slide11
How to determine if properties are good
Operational data is greatPilot plant data is goodLab data is okLiterature data is… sometimes not badPredicted data is…braveSlide12
Learn how to choose thermodynamicsSlide13
How do you choose your thermo model?
Experience with thermo is necessaryArticles / books can teach you basicsCompare to data for important systemsSlide14
Validate your thermodynamic model
Inspect TPxy diagramsRun some flash calculations & inspect resultsHave a qualitative idea of what the phase separation will look likeSlide15
Learn how to read Txy, Pxy
, Txx, xy diagramsSlide16
One step at a time!Slide17
Start simpleSlide18
Add piece-by-piece & converge at each stepSlide19
Handle recycles with careSlide20
Calculations get more complicatedSlide21
Put in a good initial estimate
Specify this flow rate to stabilize calculations!
Let the simulator calculate this
flowrateSlide22
Start off with loop open to get estimateSlide23
Common Mistakes
Matching plant dataHow accurate are the measuring devices? Last calibrated?Were all measurements taken at same steady state conditions?Are you ignoring
trace chemicals
?Neglecting to examine different conditions (cooling water can average 90˚F in Houston summer)Slide24
Other Common Mistakes
Simulators get played like a video gameConverged doesn’t mean correctUnderstand your process before modelingIf you don’t know what you’re doing, you’ll get the wrong answerThese are tools; you are the engineer Garbage in = garbage outUse engineering judgment, not
necessarily default
optionsSlide25
Takeaways from today
Process simulators are powerful tools to help make it easier to solve a wide range of engineering problemsYou will encounter these tools when you graduate & should get familiar with themLike any tool, it’s important to know how to properly use it to get the best resultsSlide26
Learn more!
Use a simulator to revisit homework problems!Find a mentor! Find examples!Learn Tpxy plots…applied thermodynamics…Read a book!Edwards, _Chemical Engineering in Practice_, kindle edition.Seider
,
Lewin, _Product and Process Design Principles_Kaes, _Refinery Process Modeling_Read a magazine article!